1. Field of the Invention
The present invention relates to apparatus and materials employed in grinding and cutting. More specifically, this invention is directed to the manufacture of abrasive materials and particularly to improved boron abrasives. Accordingly, the general objects of the present invention are to provide novel and improved articles and methods of such character.
2. Description of the Prior Art
There is a long standing desire in the art to provide improved low-cost abrasive materials for use as lapping compounds, on sandpaper, on grinding wheels, on cut-off wheels and on abrasive saws. Considering an abrasive saw as an example, standard practice in the art is to utilize cutting surfaces formed of diamond or carbide. The use of diamond or carbide materials, while resulting in tools which efficiently perform the desired cutting function, results in comparatively expensive tools which are characterized by a relatively short life.
It is well known that elemental boron, because of its unique physical properties, affords the potential of providing cutting tools of lower cost and greater life expectancy than, for example, tools which utilize a carbide cutting surface. Thus, by way of example, U.S. Pat. No. 3,619,152 suggests the employment of chopped filaments of amorphous boron in the formation of saw blanks. While elemental or amorphous boron is softer than diamond it is of comparable hardness or harder than available carbides. Amorphous boron is also considerably less expensive than diamond dust. Crystallized boron is one of the hardest materials available; beta-tetragonal and beta-rhombohodral boron being much harder than amorphous boron. Also of considerable significance is the fact that crystalline boron, when fractured, is characterized by sharp edges thus making this material more abrasive than other materials of comparable hardness.
Techniques for the production of monocrystalline or polycrystalline boron in an efficient and thus comparatively inexpensive manner have not been available in the prior art. Thus, again by way of example only, U.S Pat. No. 3,226,248 depicts a typical prior art technique for the production of monocrystalline boron. The process of Pat. No. 3,226,248 employs zone melting, controlled through the use of electron beam bombardment, and cannot be economically practiced on a commercial scale.